340 
BASIS’ OB EIO TAPt BA. 
march, in a country bristled with hills and rocks. The natives 
of San Marcellino speak of a Sierra Tunuhy, nearly thirty 
leagues west of their village, between the Xio and the' Icanna. 
La Condamine learned also from the Indians of the Amazon, 
that the Qiiiqniari conies from “ a country of mountains and 
mines.” Now, the Iqiiiari is placed hr the French astrono- 
mer between the equator and the mouth of the Xie (liie), 
which identifies it witlithe Iguiare that falls into the Icaiina! 
"We cannot advance in the geologic knowledge of America 
without having continually recourse to the researches of 
comparative geography. The sm.all system of mountains, 
which -n'e may provisionally eaU that of the sources of the 
Eio Negro and the Laup'es, and the culminant points of 
which are not probably more than 100 or 120 toises high, 
appears to e.vtend southward to the basin of Rio Tupura" 
where rocky ridges fonn the cataracts of the Rio de los 
Fnganos and the Salto Grande de Tupura (south lat. 0° 40' 
to north lat. 0° 28'), and the basin of the Upper Guaviare 
towards the west. IV e find in the course of this river, from 
(iO to 70 leagues west of San Fernando del Atababo, two 
walls of rocks bounding the strait (nearly 3° 10' nor. lat. and 
/3f“ long.) where father MaieUa terminated his excursion. 
That missionary told me, that in going up the Guaviare, he 
perceived near the strait (angostura), a chain of mountains 
bounding the horizon on the south. It is not known whether 
those mountains traverse the Guaviare more to the west, and 
join the spurs which advance from the eastern Cordillera of 
New Grenada, between the Rio Umadea and the Rio Ariari, 
in the direction of the savannahs of San Juan de los Llanos. 
I doubt the existence of this junction. If it reallv existed, 
the plains of the Lower Orinoco would communicate with 
those of the Amazon only by a very narrow- land-strait, on 
the east of the uiouiitaiuous country which surrounds the 
source of the Eio Negro : but it is more probable that this 
mountainous country (a small system of mountains, geoo-iios- 
tically dependent on the Sierra Parime) forms as it were an 
to be found in going up the Uaupes (nor. lat 0° 400 with another gold 
lake (soutli lat. 1 lOO which La Condamine calls Marahi or Morachi 
(water), and which i.s merely a tract often inundated between the sources of 
the Jurubech (Utubaai) and tlie Rio Marahi, a tributary stream of the 
Caqueta. 
